Return focus to previous app even if there are mulitple menu windows

Sometimes when Maccy menu pops up, it reports there are 2 visible menu
windows. A regular "Item-0" window that is Maccy menu and some additional
titleless NSStatusBarWindow. I have zero ideas where it's coming from
but some users reported this. In any event, we should return focus to
the previous application regardless how many menu bar windows are
visible at the moment.

Fixes #144

Author: p0deje

Maccy/Maccy.swift

@@ -16,9 +16,9 @@ class Maccy: NSObject {
   private var window: NSWindow!
   @objc private var menuLink: NSStatusItem!
 
-  private let carbonMenuWindowTitle = "Item-0"
+  private let carbonMenuWindowClass = "NSStatusBarWindow"
   private var extraVisibleWindows: [NSWindow] {
-    return NSApp.windows.filter({ $0.isVisible && $0.title != carbonMenuWindowTitle })
+    return NSApp.windows.filter({ $0.isVisible && String(describing: type(of: $0)) != carbonMenuWindowClass })
   }
 
   private lazy var preferencesWindowController = PreferencesWindowController(